When performing surgical procedures on the heart, it can be advantageous and/or necessary to interrupt the normal operation of the heart. In fact, it is often necessary for cardiac surgery to use cardiopulmonary-bypass techniques and to isolate the heart from its source of blood supply. One technique for preparing the heart for surgery in this way is to infuse cold cardioplegic fluid to cool and stop the beating of the heart. Cardioplegia can be administered in an antegrade manner (i.e., through the arteries and in the normal direction of blood flow), in a retrograde manner (i.e., through the veins in the opposite direction of normal blood flow) or in a combination of antegrade and retrograde manners. Due to some of the risks and inconveniences of antegrade cardioplegia, particularly for aortic valve replacement, many surgeons prefer to utilize the techniques of retrograde cardioplegia.
Typically, retrograde cardioplegia is administered by inserting a balloon catheter into the coronary sinus area, inflating the balloon to stop the normal flow of blood into the right atrium, and perfusing the cardioplegic solution through the coronary veins in the opposite direction of blood flow. In order to insert the balloon catheter into the coronary sinus area, both the superior and inferior venae cavae must be tied and each must be cannulated, thereby isolating the right heart. The right atrium may then be opened without allowing the dangerous introduction of air into the circulatory system. Once the right atrium is open, the catheter can be inserted into the coronary sinus under direct visualization while the cardioplegic solution is administered. After this occurs, the right atrium can then be closed. This sequence of steps can be performed for each administration of cardioplegic fluid during a particular surgical procedure.
In order to have access to the heart for this direct visual placement of a catheter, many commonly used delivery methods require the creation of a large incision in the chest cavity to expose the heart. However, techniques have recently been developed to place these devices in the coronary sinus area in a more minimally invasive manner in order to lessen the trauma to the patient and the risks associated with relatively large incisions. Because direct visualization is not possible through the incision site when using these less-invasive types of surgery, other devices and methods have been developed to detect and monitor the placement of the catheter within the body. For example, a portion of a catheter can be echogenically enhanced so that it can be ultrasonically imaged and guided to the desired location in the heart of the patient, such as is described in U.S. Pat. No. 5,967,988 (Briscoe, et al.), which is commonly owned by the assignee of the present invention. One technique that can be utilized for such imaging involves transesophageal echocardiography (TEE), which can often provide the information necessary for proper navigation and location of the catheter. In other cases, however, the available TEE devices and methods do not provide sufficient information due to situations such as the use of devices that become undetectable when using 2-dimensional images of the TEE probe. Thus, there is continued desire to provide improved devices and methods for accurately and reliably visualizing remotely placed devices, such as portions of a retrograde cardioplegia cannula. It is further desirable to provide a trans-thoracic retrograde coronary sinus perfusion cardioplegia cannula that is visible using trans-esophageal echocardiography and fluoroscopy.